World Trade Center

The World Trade Center (sometimes informally the WTC or Twin Towers) was a seven-building complex in Lower Manhattan (New York City) that was destroyed in the September 11 attacks. The World Trade Center was designed by Minoru Yamasaki who used an innovative tube-frame structural design for the twin 110-story towers. The elevator system in the towers utilized large-capacity express elevators which went to sky lobbies, along with local elevators serving individual floors. In gaining approval for the project in the early 1960s, the Port Authority of New York and New Jersey agreed to take over the Hudson & Manhattan Railroad which became the Port Authority Trans-Hudson (PATH). Groundbreaking for the World Trade Center took place on August 5, 1966. The North Tower was completed in December 1970 and the South Tower was finished in July 1971. Construction of the World Trade Center involved excavating a large amount of material which was used in making Battery Park City on the west side of Lower Manhattan. The complex contained 13.4 million square feet (1.24 million m²) of office space. An observation deck was located atop the South Tower, while the Windows on the World restaurant was located at the top floor of the North Tower. With construction of 7 World Trade Center in the 1980s, the World Trade Center had a total of seven buildings but the most notable were the main twin towers which were each 110 stories tall. During a press conference in 1973, Minoru Yamasaki was asked "Why two 110-story buildings? Why not one 220-story building?" His response was: "I didn't want to lose the human scale". When completed in 1972, 1 WTC became the tallest building in the world, unseating the Empire State Building after a 40-year reign. 1 WTC (the North Tower, which featured a 360-foot (110 m) high TV and radio antenna added in 1978, stood 1,368 feet (417 m) high at the top of the roof. With the 360 ft antenna, the highest point of the North Tower reached 1,727 ft. 2 WTC became the second tallest building in the world when completed in 1973. The observation deck was 1,362 feet (415 m) high. The World Trade Center towers held the height record only briefly. Chicago's Sears Tower, finished in May 1973, reached 1,450 feet (442 m) at the rooftop. Of the 110 stories, eight were set aside for technical services (mechanical floors) Level B6/B5, Floors 7/8, 41/42, 75/76 and 108/109, in four two-floor areas evenly spaced up the building. All the remaining floors were free for open-plan offices. Each floor of the towers had 40,000 square feet (3,700 m2) of space for occupancy. Each tower had 3.8 million square feet (350,000 m²) of office space. Altogether the entire complex of seven buildings had 11.2 million square feet (1.04 km²) of space.